Dissimilar materials may be joined together to form an electronic device enclosure or other composite structure. The composite structure may exhibit material properties of one or both of the materials. For dissimilar metals, such composites may be susceptible to brittle fracture or other failure modes at a joint or bonding region between the dissimilar materials. For example, directly joining (e.g., welding) dissimilar metals having different melting temperatures, electrical or thermal conductivities, and/or tensile strengths may contribute to the production of brittle intermetallic compounds.